Soundboard for pianos



Feb.'8, 1938. P. H. BILHUBER SOUNDBOARD FOR PIANOS Filed Nov. 24, 1956 m n M WW n z 1/ m 7 .py j m H w Patented Feb. 8, 1938 UNITED STATES PATENT OFFICE SOUNDBOARD FOR PIAN OS tion of New York Appcation November 24, 1936, Serial No. 112,558

6 Claims.

This invention relates to soundboards for pianos.

The object of the invention is to increase the vibrating area of a soundboard particularly within the size limits of small grand or upright pianos.

A further object is to provide additional length to the longitudinal grain of the Wood of the soundboard without increasing the size (length or height) of the piano case or frame.

A further object is to increase the acoustic compliance of the soundboard to the loW frequencies imposed upon it.

Finally, the object is to overcome the stiiness of the soundboard at and near the region of the two soundboard bridges.

The invention consists of an improved soundboard in which an augmenting portion serves to increase the Vibrating area of the soundboard, the length of the long grain being at the same time increased, without however increasing the size, that is the length of the piano case or frame. An embodiment of this invention provides the main soundboard provided at its rear with a floating rim, that is, this rim is not secured to the piano case, and to the oating rim is secured an augmenting soundboard which has its base portion supported by the piano case. In another embodiment, this main soundboard and auginenting soundboard is a convex-concave shape invoking the advantages of such shapes, as pointed out in Patent No. 2,051,633 dated August 18, 1936, and in my pending application Serial No. 67,627 led March 6, 1936.

Other features of the invention will be hereinafter described, and embodiments of the invention will be shown in the drawing and the invention will be finally pointed out in the claims.

In the accompanying drawing:

. o Figure l is a plan View of my improved soundboard applied to a piano case,

Figure 2 is a sectional View taken on line 2 2 of Figure 1,

Figure 3 is a sectional View taken on line 3 3 of Figure 1,

Figure 4 is a sectional View taken on line 4 4 of Figure 1, and

Figure 5 is a perspective view of a spacing block.

Referring to the drawing, and more particularly to Figure 1, the piano `case I!! has the usual grand piano shape. It is, as is known, provided at its interior with a supporting rim portion formed of a shoulder II, extending almost entirely around the inner part of the case.

'I'he main soundboard I 2 rests at its edge along almost its entire periphery upon this shoulder I I, excepting the front part I3 of the soundboard. This soundboard is preferably of convex concave shape. The soundboard I2 is so constructed that the grain of the wood runs in the general direction of dot-dash line I5 I5.

The rear portion of the main soundboard I2 does not rest upon the shoulder II, as this shoulder is cut away at a certain part of the case I0, so as to form, a lower shoulder I4, as shown in Figure 2.

The rear portion of the main soundboard I2 being free of the shoulder I I is suspended in the air. To this rear portion is secured by glue or they like a rim I6 which abuts against the lower surface of the main soundboard. As the rim I6 is unsupported except by the lower or augmenting soundboard I 'I, it can be called a floating rim. To this floating rim i6 at the underside thereof is glued or otherwise Secured, the augmenting soundboard il, which extends forwardly from the floating rim and is supported at its front e-nd by a crossbar I9 resting upon a bottom wall 20 of the piano case. The crossbar I9 has its ends fastened to the rim portions II of the piano case. This augmenting or partial soundboard extends across the entire rear width of the piano case. Upon the end portions of the shoulders Il, there is placed a block 22 of wood,

which has a wider portion 23 and a narrower portion 24. The wider portion 23 rests upon the shoulders I I, and the narrower portion 24 extends between the upper and lower soundboards and against the floating rim I6. This block acts as a connection between the piano casing and the floating rim. On the upper right hand side of Figure 1 is shown the block 22 inserted, and on the upper left hand View is shown the gap 22a for a block 22 to be inserted. The bers of the Wood of the partial diaphragm run in the same direction as those in the longer or main soundboard, as indicated by the dot-dash line I5-I5 of Figure 1, and this feature adds to the increased vibration attained from the main and augmenting soundboards.

The augmenting soundboard Il acts with the floating rim I6 and upper or main soundboard to provide a freely acting and resilient soundboard. In effect, the upper soundboard has been increased in area by the presence of the lower soundboard. The lower or augmenting soundboard acts as an extension of the main soundboard.

At the overhanging end of the soundboard, the

usual anchorage for the string-frame or piano plate 3U shown in Figure 4, is provided by the customary lagscrew 3! which secures the stringframe against the dowel pins 32 embedded in holes 34 of the rim portion I4. The lagscrew 3l and dowel pins 32 are provided with clearance 35 from the floating rim l5 and soundboards l2 and i? fastened thereto, by means of notches or holes in the latter, in order to prevent any contact or restriction of vibration of the soundboard by the lagscrew or dowel pins. This plate, dowel pins and lagscrews are known and have been described to show the preferred form thereof used in connection with the invention described, the novelty here being the clearance notches.

In Figure 2 is shown the known plate 3S held in position on the frame of the piano by screws or bolts Si, and to which the string 38 is secured. This string 38 passes over the bridge 3T. The plate 38 has also the string 40 secured thereto, and this string 4D passes over the bridge 39. The bridge 3i is the bass bridge, and the bridge 39 is the treble bridge. All of these parts, by themselves considered, are well-known.

The preferred form of soundboards to be used, is that of convex concave shape. In Figure 2 the greatest thickness of the main soundboard is at A which tapers to the rim or where it is glued to the floating rim I 6, and the greatest thickness of the augmenting board is at B which tapers to its rim at b, where it is glued to the floating rim. The augmenting soundboard is iexed in a manner similar to the main soundboard.

Thus, the overhanging part of the composite soundboard is freely more movable without imediment in a resilient manner, and acts as one soundboard in respect to the vibrations desired. The augmenting soundboard is iiexed in a manner similar to that shown in my patent and application.

It will be seen that a means to control the stiffness of the main soundboard is utilized by providing means for increasing the area of the board. The area and resiliency eixected are proportioned to the size of the piano case and proportioned to the degree of compliance required of the soundboard for more efficiently propagating vibrations in the lower acoustic frequencies.

It has been customary to construct a so-called suspension type of bass bridge which is affixed to the soundboard a considerable distance from the edge thereof, and to extend this bridge parallel to said soundboard towards the outer edge, at which point connection is made to the strings. A great loss in vibroinotive transmission occurs in this structure because the bridge tends to twist rather than to directly propagate the string vibrations into the soundboard in a direction perpendicular to the surface thereof.

The improved construction obviates the necessity of resorting to the so-called suspension type of bass bridge and makes possible far greater acoustic response, since the composite soundboard provides a resiliency and thereby overcomes the stiffness which is present in the conventional soundboards described above.

Having thus described my invention which is applicable to small grand, upright and square pianos, and the embodiments thereof, I do not wish to be limited to the particularities thereof, and desire to include such changes as may be made without departing from the spirit of my invention, as dened in the appended claims.

I claim:

i. A soundboard for pianos, comprising a main soundboard having a curved end, said soundboard being supported upon the piano case and having its curved end free thereof, an augmenting soundboard having a curved end, said lastnanied soundboard supported upon the piano case and having its curved end free thereof, and a floating rim between the curved ends of said soundboards, the rim being in contact with both soundboards, the two overhanging soundboards and floating rim therebetween, forming a freely suspended and vibrating member, the augmenting soundboard acting as a continuation of the main soundboard, said soundboards being of concave convexo shape with the edge portions tapering, and having said tapered edge portions in contact with the rim.

2. A soundboard for pianos, comprising a main soundboard having a curved end, said soundboard being supported upon the piano case and having the curved end of the piano free thereof, an augmenting soundboard having a curved end, said soundboard being supported upon the piano case and having the curved end free thereof, a floating rim between the curved ends of said soundboards, said rim contacting with both soundboards, the two overhanging soundboards and floating rim therebetween, forming a freely suspended and vibrating member, the augmenting soundboard acting as a continuation of the main soundboard, and blocks supported on the piano case and extending between the main and augmenting soundboards, said soundboards being of concave convexo shape with the edge portions tapering, and with said edge portions in contact with the rim.

3. In combination with a piano case having a curved end and having a shoulder extending partially around said case and provided with a cut out lower than said shoulder at the curved end of the piano case, a main soundboard supported on said shoulder and having a curved end overhanging said cut out and free of the shoulder, a cross bar supported by the piano case approximately at the termination of said shoulder; a second soundboard having its base portion supported on the crossbar and extending with its edge over the cut out and having a curved end, a rim secured to the overhanging edges of the two soundboards, and blocks supported by the shoulder and extending between the edges ci the two soundboards and in alignment with the rirn, whereby the overhanging soundboards act as extensions to each other at the curved edge portions of each other, said soundboards being of concave convexo shape with the edge portions tapering, and with the rim in contact with said tapered edge portion.

fi. A composite soundboard ior pianos having a piano case, a string frame, a lag screw and dowel pins, said lag screw and dowel pins connecting the string frame with the piano case, consisting of a main soundboard, an augmenting soundboard, both soundboards being of convexo concave shape and tapering toward the ends thereof, and a rim interposed between said tapering ends and contacting therewith, said soundboards and rim portion being notched for the passage of the lag screw and dowel pins.

5. In a piano, the combination with a soundboard consisting of a main soundboard of convex concave shape tapering to its edge, an augmenting partial soundboard of convex concavo shape tapering to its edge, and a floating rim therebetween and contacting with the tapering edges, ai;

the rear of the piano case, of a. bridge placed on the rearmost end of the main soundboard, and a string frame at the rear of the bridge supported by the piano case for the strings passing over the bridge, whereby a direct connection of the bridge and main soundboard nearest the rearmost edge of the main soundboard is effected.

6. In a piano, the combination with a soundboard consisting of a main soundboard of convex concavo shape tapering to its edge, an augmenting partial soundboard of convex concavo shape tapering to its edge, and a floating rim therebetween and contacting with the tapering edges, at

the rear of the piano case, of a. bass bridge placed on the rearmost end of the main soundboard, a string frame at the rear of the bridge supported by the piano case for the strings passing over the bridge, and a treble bridge disposed at a distance forward of the bass bridge, whereby a direct connection of the bass bridge and main soundboard nearest the rearmost edge of the main soundboard is effected and the treble bridge is Cgi placed at the greatest distance from the bass 10.

bridge.

PAUL H. BILHUBER. 

